Gas fractionating apparatus and method



Feb. 13, 1951 CORNELlUs 2,541,409

' GAS FRACTIONATING APPARATUS AND METHOD Filed June 7, 1945 2 Sheets-Sheet 1 o l E"L .1

vuch {01, Richard T. Cornelius Feb. 13, 1951 R. T. CORNELIUS 2,541,409

GAS FRACTIONATING APPARATUS AND METHOD Filed June 7, 1943 2 Sneets-Sheet 2 'L'L a ii a nywaw'im Richard T. Cornelius Paemesret. 13,1

OFFICE GAS FRAC TIONATING APPARATUS AND METHOD Richard T. Cornelius, Minneapolis, Minn.

Application June "I, 1943, Serial No. 489,886

14 Claims. (Cl. 62-123) an apparatus particularly adapted to separate I an exceedingly high percentage of the oxygen from the atmosphere.

Another object of the invention resides in providing an apparatus which will be entirely automatic in its operation, thus adapting the apparatus to various uses where skilled labor is not available and where constant attention is not possible.

A still further object of the invention resides in providing a process for the separation of oxygen from the air by liquefaction in which a relatively high thermodynamic efficiency is procured and in which the power consumption is a minimum.

Another object of the invention resides in providing an apparatus which is capable of operating continuously without interference from condensation of the water vapor and carbon dioxide contained in the air being fractionated.

An object of the invention resides in providing an apparatus free from danger of explosion due to combustion of the vapors of lubricants at high pressures.

Another object of the invention resides in pro viding an apparatus which will effectively operate at various atmospheric pressures, such as would be encountered by aircraft in changing altitude.

A further object of the invention resides in providing an apparatus which will operate at a relatively low pressure, for example, four or five atmospheres.

An object of the invention resides in providing fractionating apparatus which will be light in weight, compact and portable.

A feature of the invention resides in the use of an automatic control to regulate the operation of the air expander and thereby keep the system thermodynamically balanced.

Another object of the invention resides in providing a rectification apparatus and proces in which the first stage of rectification is carried out coincident with the preliminary condensation of the air in a manner wherein the products of the first stage of rectification are readily separated and controlled.

Another object of the invention resides in producing fractionation by liquefying the air and its constituents and in accurately dividing the liquids in accordance with their requirements for use in the apparatus.

A feature of the invention resides in providing metering tubes in the liquid reservoirs adapted to divide the liquids into separate portions or streams of substantially fixed volumetric ratio.

Another object of the invention resides in providing an apparatus in which the impurities of the air are removed without chemical process.

An object of the invention resides in providing an apparatus in which impurities of the air such as condensed water and carbon dioxide are evaporated by exhaust gases passing through the conduits in which the impurities are deposited.

Another object of the invention resides in providin a counterflow heat exchanger having three conduits, in which the supply of compressed air to be fractionated is run through one of the conduits in one direction, the separated oxygen in another of said conduits in the opposite direction, and the remaining exhaust gases is run through the third conduit in the same direction as the oxygen, and in which the conduits in which the air and exhaust gas are run is alternated by valves which operate to produce a continuous timed cycle of operation.

A still further object of the invention resides in providing a system in which no lubricant is needed.

A feature of the invention resides in utilizing a diaphragm compressor or compressors and a diaphragm air expander in the system.

Other objects of the invention reside in the novel combination and arrangement of parts and in the details of construction hereinafter illustrated and/or described.

In the drawings:

Fig. 1 is a diagrammatic view of an air fractionating apparatus illustrating an embodiment of my invention. v

Fig. 2 is a cross sectional detail view of one of the metering tubes of the invention.

Fig. 3 is a diagrammatic view similar to Fig. 1

. of a modification of the invention for the use solely in the production of oxygen.

Inasmuch as the drawings are diagrammatic, no attempt has been made to show the details of construction of the parts or thermal insulation which is, of course, applied between all component parts which operate at considerable differences of temperature.

In my improved air fractionatin apparatus, air

- is compressed by a compressor I B and passe 4 are arranged two metering tubes 83 and 48 which are similar to the tubes 36 and 31 and which divide the liquid collected in reservoir 42 into two streams having fixed volumetric ratio.

All of the metering tubes 36, 31, 43 and 44 are similar in construction and only tube 3S, which and 2|, where these gases cool the incoming air.

The rectifier H consists of a case 22 which is provided with a number of staggered baffles 23 connected to the walls of the case and disposed throughout the major portion thereof and spaced from said walls at opposite localities to provide a tortuous passageway therethrough. These bafiles form trays arranged to hold a shallow body of liquid with a large amount of exposed surface,

Liquid supplied to an upper tray will cascade from one tray to another and gas forced through the column will pass over the surface of the liquid of successive trays in intimate contact therewith..

Within the lowermost portion of the case 22 of rectifier II is arranged a reservoir 35 which is disposed beneath the lowermost baille 38 of said rectifier and receives the liquid discharged therefrom. This reservoir does not occupy the entire space of the case 22, so that the interior of the said case is still in communication with the interior of the tubes 29 of the evaporator condenser I3. The reservoir 35 is provided with two metering tubes 36 and 31. These tubes cause'a uniform division of the liquid in the reservoir and produce two streams of liquid of substantially fixed volumetric ratio.

The rectifier I2 is constructed similar to the rectifier II, being provided with .a case 28 and similarly arranged baiiles 25 therein.

The evaporator condenser I3 consists of a case 26 having two partitions 21 and 28 therein to which are attached the ends of a number of vertically arranged tubes 29 and I23. The case 26 is connected to the case 220i rectifier I i and also to the case 24 of rectifier I2. It will be noted that the tubes 29 communicate at their upper ends with the interior of rectifier I I and are separated at their lower ends by means of a wall 3I from the interior of the rectifier 12. The evaporator condenser I3 is constructed so that a passageway is formed surrounding the tubes 29 which is independent from the passageways through said tubes and which communicates with passageways 33 and 34 at the ends of the evaporator condenser.

The upper ends of tubes I23 open into chamber I I9 which is separated from the rectifying column II by partition H1. The lower ends of tubes I23 open into a chamber I 2I which is separated by means of a partition II8 from chamber I22 immediately below tubes 29, said chamber being separated from rectifying column I2 by'partition 3I. The lowermost portion of the case 26 of the evaporator condenser I3 has a jacket 39 which provides a passageway 4| communicating with the passageway 33. Passageway M is in communication with the interior of the rectifier I2.

A partition 32 is placed between the tubes I23 and the case 26 and is connected to partition 28 so that condensate collecting around the tubes I23 and 29 will flow in the direction of passageway 34. The lower end of passageway 34 communicates with a passageway 216 which, in turn, communicates with a reservoir 42 located just above the trays 25 in column I2. In the reservoir 42 is shown ,in detail in Fig. 2, will be described.

The tube 36 is received within a housing I16 which consists of two side walls I11 and I18, a rear wall I19 and two flanges I8I issuing from the endsof the side walls and spaced from one another-to leave a longitudinal vertical opening 82 therebetween. The flanges I8I have converging inner surfaces I83 which extend up to the opening I82. The tube 36 consists of a thick rigid rear wall I84 with two thin flexible side walls I85 connected thereto. Two flanges 136 issue angularly therefrom and are spaced from one another at their extreme ends to form a narrow vertical slot I81. The flanges I86 ride upon the surfaces I83 of flanges I8I and when the tube 36 is urged :toward the opening I82, the flanges I86 are forced together so as to close the slot I81. For this purpose, one or more screws I88 are employed which are screwed into bosses I89 formed on the rear wall I18 of housing I16 and which engage the rear wall I84 of tube 36 and force it against the surfaces I83 of housing I16 and force the flanges I86 together to reduce the width of the slot I81. By proper adjustment of the slots I81 of the tubes 36 and 31, the proper proportion of liquid may be discharged from each tube.

While it may be desirable to have all of the metering tubes 36, 31, 43 and 44 adjustable, it can readily be comprehended that one only of each pair may be made adjustable, the other tube of the pair having a fixed slot, or if the proportions and capacity be accurately determined, the slots of all of the tubes may be fixed.

The metering tubes are arranged in their respective reservoirs so that the lowermost ends of the slots are at the bottom of the reservoir or at the same height above the bottom and so that the said slots extend above the maximum height of the liquid. Also, the slots are arranged in facing relation, being relatively close together to avoid inaccuracy in metering in the event of til ing of thecolumn ID. The metering tubes are used in pairs and the vertical slot in each tube is of uniform width throughout its height. The width of the slot in each metering tube of a pair is in an exact relationship with the width of the slot of the other metering tube, so that the flow orifice areas of each of the two slots remain in a constant and uniform proportion, regardless of the height of liquid in the reservoir. The result of this construction is that a fixed volumetric ratio of flow through the tubes of each pair is established. This exact ratio of flow will remain the same regardless of the total volume of liquid collected in the reservoir. This feature of construction is very vital in securing automatic oper ation of the apparatus under varying conditions.

In the lowermost portion of the case 24 of rectifier I2 is formed a reservoir I53 which has an outlet I54 adapted to be closed by a valve I55.

A float I56, controlled by the height of the liquid in the reservoir I53, operates valve I55. The outlet I54 is connected by means of a pipe I51 with the case 22 and communicates with the interior of said case at an elevation intermediate the upper and lower ends of said case.

Disposed exteriorly of the rectifier II is a reservoir I59 for liquid which has an outlet I6I at 78 the lowermost portion thereof. This outlet is adapted to be closed by means of a valve I62 which is controlled through a float I63 disposed in said reservoir which is operated by the elevation of the liquid within said reservoir. The lowermost portion of the reservoir I59 has connected to it a pipe I68 which communicates with the metering tube 36 in reservoir 35 of rectifier II. An equalizing pressure vent I69 communicates with the reservoir I59 at a point above the maximum elevation of the liquid in said reservoir and with the interior of the case 22 of rectifier II below the reservoir 35. The outlet IBI of said reservoir is connected by means of a pipe I1| with the chamber |2I of the evaporator condenser I3. The other metering tube 31 in the reservoir 35 communicates directly with the interior of the case 22 and discharges into a reservoir I29 to be subsequently described.

A reservoir I64, similar to reservoir I59, is employed which is disposed exteriorly of the rectifier I2 and which has an outlet I65 closed by a valve I66 and operable by a float I61. The metering tube 43 in reservoir 42 discharges directly into the upper portion of reservoir I64, while the outlet from-said reservoir is connected by means of a pipe I12 with the case 22 of rectiher I I at the uppermost portion thereof. A passageway 282 communicates with the upper portion of reservoir I64 and the interior of column I2 at its upper end and serves as a pressure equalizing passageway to permit a free flow of liquid into said reservoir.

In the evaporator condenser I3 is formed the reservoir I29 previously referred to, which communicates with the space above the tubes 29 and at its lower end with the interior of chamber I22, by means of a tube I3I. In the reservoir I29 is mounted a float I32 which operates a valve I30 including a sliding valve member I33. Valve member I33 is in the nature of a piston which is connected to a piston rod I96 and is slidable in a cylinder I91. The piston I96 is guided for sliding movement in a guide I98 connected to the cylinder I91 and supported by the reservoir I29. The cylinder I91 is formed with three ports I34, I35 and I31, the ports I34 and I35 being disposed in juxtaposition at the side of the cylinder intermediate the ends thereof, while the port .I31 is at the far end of the cylinder and is connected by means of a pipe I99 with the case 22 of rectifier II, intermediate the upper and lower ends thereof. The valve I33 is operable to bring the two ports I34 and I35 into communication or to prevent flow therebetween. Valve I33 has a passageway I36 through the same which communicates through the port I31 and pipe I99 with the interior of the case 22 of rectifier II. The gas from any leakage that may escape past the walls of piston I33 is vented through passageway |36 and does not affect the movement of piston I33.

The compressor I6 is of the diaphragm type, has a case 45 and a diaphragm 46 operated by means of a crank 41 through a connecting rod 48. Case 45 is provided with an air inlet 49 and an air outlet 5| controlled by suitable valves.

The air cooler I1 comprises a case 52 having a coil 53 therein. Cooling water is directed into the coil 53 by means of a pipe 54 and leaves the said coil through a drain pipe 55.

The air to be separated into its constituent gases is drawn into the case 45 of the compressor I6 through inlet 49 and leaves through outlet 5|, being directed into the bottom of the case 52 controls the flow of liquid through the trap I92.

When the liquid in trap I92 reaches a certain level, the surplus drains out through an overfiow pipe I94 which is connected to the drain pipe 55. This trap serves to remove a. certain proportion of the water of the air to be fractionated which condenses out of the air on the compression and subsequent cooling thereof.

The valve mechanism I8 consists of two cylinders 58 and 59 having coaxial bores and provided with a piston rod or valve stem 6| carrying two pistons or valve members 62 and 63 operable in cylinder 58 and four pistons 64, 65, 66 and 61 operable in cylinder 59. The cylinder 58 has a centrally located port 68 and two spaced ports 69 and 1|, one on each side of the central port. The cylinder 59 has a central port 12 and two ports 13 and 14 corresponding to the ports 69 and 1|. In addition, the said cylinder has two other ports 15 and 16 which are spaced apart a distance greater than the two ports 13 and 14, and which are disposed one on each side of the port 12. The pipe 51 is connected to two branch pipes 11 and 18 which are respectively connected to the ports 68 and 12. The two ports 15 and 16 are both connected to a common passageway 19 which is connected to a pipe 209. This pipe may be connected to a gas collection system which has not been shown in the drawings.

The heat exchanger I9 consists of two conduits BI and 82 which are of appreciable length and/or area and which are in intimate heat-conducting relation with respect to one another. In the drawings, this heat exchanger has been shown as having two conduits, though it can be readily comprehended that two sets of conduits connected together in any suitable manner, may be used in place thereof. The conduit 8| is connected to port 69 and the conduit 82 to port 1| of cylinder 58 of valve mechanism I8.

In the heat exchanger 2| are employed three conduits 84, 85 and 86, all in heat-exchanging relation with respect to one another. The conduits 84 and 65 may be formed by means of two tubes in heat conducting relation with respect to one another and surrounded by an outer tube which forms the conduit 85 which extends about and is in heat-conducting relation with respect to both of the conduits 84 and 85. Conduit 84 is connected to ports 13 and conduit 85 is connected to port 14 of the cylinder 59 of valve mechanism I8.

While I have shown the heat exchanger 2| constructed with two juxtaposed tubes arranged within a third, it can readily be comprehended that any other suitable construction, such as is now known in the art, may be used.

The heat exchanger I4 consists of a case 81 in which are disposed three coils 88, 89 and 9|. The coils are placed so that the air flowing through case 81 contacts the inlet end of each coil first. Case 81 and coils 88, 89 and 9| can be replaced with any other construction which would provide the necessary amount of heat transfer surface placed in the same general relationship. All of these coils are in heat-conducting relation with respect to the gas or liquid which may flow through the case 81.

Connected to the heat exchanger I9 is a valve of the cooler I1 by means of a pipe 56. Case mechanism 92. This valve mechanism consists of a housing 98 having a partition 94 therein tormingwithin said housing three chambers 95, 88 and 81. Two valves 88 and 99 control communication between the chamber 91 and the chamber 95 and between the chamber 91 and the chamber 96. These valves are automatic and operate in alternation. The chamber 95 has a port IOI, while the chamber 96 has a port I02. These ports are normally closed by spring-controlled valves I03 and I04. The conduit 8I of heat exchanger communicates with chamber 95, while the conduit 82 of said heat exchanger communicates with the chamber 96.

The heat exchanger 2| has connected to it a valve mechanism I similar to the valve mechanism 92. This valve mechanism includes a housing I08 and parttion I01 forming in the housing chambers I08, I09 and H0. Alternately operable valves III and H2 bring the chamber IIO into communication with the chambers I08 and I09. Spring-operated valves H3 and H4 bring .the chambers I08 and I09 into communication with outlet'ports us and us. The conduit 84 of heat exchanger 2I communicates with chamber I08, while the conduit 85 of said heat exchanger communicates with the chamber I09.

The expansion engine I5 is of the diaphragm type and is provided with a case I40, a diaphragm I42 associated therewith and is operable through a connecting rod I M and a crank I43. Case I40 has an outlet I44 and an inlet I46. The valve mechanism of the expansion engine I5 may be operated by cams or in any other suitable manner. There must be connected to the output shaft of the expansion engine a device which provides a load of uniform torque characteristics, regardless of the speed of the engine. This device is not shown on the drawings, but could consist of an electrical generator for work recovery. On small units, the recovered work is of little value and the work of the expansion engine can best be absorbed by a friction .device located exteriorly of heat insulation used to contain the expansion engine.

The oxygen is removed from the apparatus at a pressure below atmospheric. For this purpose,

a compressor I14 is utilized. This compressor is of the diaphragm type and is similar to compressor I6. This compressor raises the pressure up to that necessary to fill tanks or supply oxygen consuming apparatus. Since diaphragm compressors operate without lubrication, the danger resulting from highly compressed oxygen and lubricating oil is entirely eliminated. The outlet pipe I15 of the compressor I14 is connected to any desired collection or consumptive system for oxygen.

Th various parts of the iractionating apparatus of my invention are connected to one another in the following manner.

The upper end of the coil 89 of heat exchanger I4 is connected by means of a pipe I21 with the upper end of the case 22 of rectifier II. The lower end of this coil is connected by means of a pipe I28 with both of the ports H5 and H6 of valve mechanism I05. Outlet I44 of expansion engine I5 is connected by means of a pipe I45 with the upper end of the coil 9|. Inlet I46 of said expander is connected by means of a pipe I39 with the port I35 of cylinder I91. The lower end of the coil ill of heat exchanger I4 is connected by means of a pipe I41 with both of the ports IOI and I02 of valve mechanism 92. The chamber II9 of evaporator condenser I3 is connected by means of a pipe I25 with the upper end or the 001188 or heat exchanger I4, while the lower end of said coil is connected by means or a pipe I26 to the upper end of the conduit 88 of heat exchanger 2I. Conduit. 86 or heat exchanger 21 is connected at its lower end by means ot a pipe I13 to the compressor "4. The case 81 of the heat exchanger I4 is connected at its upper end with a pipe I48, which, in turn, is connected with the valve mechanism I05 and communicates with the chamber IIO thereof. The lower end of the case 81 of heat exchanger I4 has two outlets 203 and 204 communicating with pipes I49 and I52, respectively. Outlet 208 is located lowermost in case 81 of heat exchanger I4 and discharges therefrom any condensate formed by coils 88', 89 and BI in heat exchanger I4. Condensate flowing from outlet 203 passes through pipe I49 and enters rectifying column I2 at a point approximately half way between the bottom and top of the trays 25 contained therein and cascades over the lower half of the trays to the bottom of the column. The pipe I49 is formed at I5I in the shape of a liquid trap to prevent the fiow of vapor through pipe I49. Air which is not condensed in heat exchanger I4 passes through outlet 204 located near the bottom of case 81 and thence through a pipe I52 to the lower end of column I2 at a point below the trays 25. e

In describing the operation of the apparatus, I will first assume that the apparatus is in operation at full capacity and that all component parts have reached a state of equilibrium. The figures which will be given are based on ideal conditions such as would be obtained if the design and construction of the apparatus were of the highest order and are only approximate.

I will describe first the operation of column I0. Reservoir 35 is partly filled with liquid oxygen of high concentration. The boiling point of this liquid oxygen is determined by the pressure in the rectifier II which is maintained close to atmospheric pressure by the gas collection system attached to pipe 200 which communicates with rectifier II through the valves and conduits previously described. The boiling point of this liquid oxygen would be -183 C. As there is no input of heat into the reservoir 35, the liquid oxygen does not boil, but flows through meterin tubes 36 and 31. Metering tube 36 is proportioned to discharge by gravity 21% of the available liquid into reservoir I59. The remaining 79% of the liquid oxygen being discharged through metering tube 31 into reservoir I29. The oxygen discharged into reservoir I29 passes through the tube I3I and into the interior of tubes 29 where it is caused to boil at 183 C. as will be presently described. The oxygen in reservoir I59, after filling the reservoir and lifting the float I63, flows through tube I1I into the interior of tubes I23. The space above the tubes I23 is kept at a pressure a little below that in the rectifier II by pump I14, so that the boiling point of the liquid oxygen in these tubes will be a little lower than 183 C. Float valve I62 maintains a continuous pressure seal between the interior of tubes I23 and the interior of rectifier II, with the result that at no time, regardless of the action of pump I J 4, can any gas or fluid be drawn by pump I14from rectifier I I, except that which passes through metering tube 36. This is essential to preserve the balance of the column under various operating conditions.

The heat required to vaporize the oxygen in tubes I 23 and 28 is supplied by relatively pure 9 I nitrogen gas under pressure which surrounds the tubes. Since the pressure in rectifier II is atmospheric, the temperature of the liquid oxygen in the interior of the tubes I23 is +183 C. In the rectifier I2, the pressure is four atmospheres. However, at four atmospheres pressure and 182 C., nitrogen liquefies. Hence, with a slight temperature difference between the nitrogn gas in rectifier I2 and the liquid oxygen in rectifier II, a heat transfer takes place and the oxygen in tubes I23 is evaporated and the nitrogen gas about said tubes is condensed. Since the temperature at which liquefaction of the nitrogen occurs can be controlled by varyin the pressure, the compressor I6 is operated at a pressure such as to produce the results above referred to. The nitrogen gas that surrounds the tubes I23 and 29 enters the evaporator I3 through passageway 33 and contacts tubes I23 before reaching tubes 29. This fact, together with the fact that the oxygen in tubes I23 boils at a little lower temperature than the oxygen in tubes 29, due to the reduction in pressure caused by compressor I14, causes all of the oxygen in tubes I23 to be evaporated first, and insures the complete removal of all oxygen liquid flowing through metering tube 36. This feature is utilized to secure automatic operation under all operating conditions.

The oxygen gas vaporized in tubes 29 rises in rectifier II and passes progressively over the trays 23 in the rectifier, said trays being covered by a cascading reflux liquid which enters the rectifier as will be presently described. At the top of rectifier I I, relatively pure liquid nitrogen enters through pipe I12 and cascades downwardly over trays 23. The boiling point of the liquid nitrogen at the pressure maintained in rectifier i I is 195 C. This is 12 C. lsss than the boiling point of the oxygen in the lower end of the rectifier II. As the oxygen gas rises in the rectifier and passes over the trays, it contacts a colder fluid. The result is that part of the oxygen gas condenses, giving up its latent heat to the colder liquid. The latent heat given to the colder liquid in the tray vaporizes some of this liquid because it is more volatile and is warmed above its vaporization temperature. The action described is progressive in nature, so that by the use of a sufficient number of trays, the bottom tray will contain practically pure liquid oxygen at l83 C. and the top tray will contain practically pure liquid nitrogen at l95 C. Intermediate trays will contain mixed liquids having a larger percentage of nitrogen towards the top and a larger percentage of oxygen towards the bottom. The boiling points of the mixed liquids in'the various trays will also progressively increase from top to bottom. As the oxygen gas rises through the rectifier II, it is gradually replaced by nitrogen gas as described above, so that before it reaches the top of the rectifier, the replacement has been complete and pure nitrogen gas is discharged by pipe I21.

In the actual operation of the apparatus, more liquid in the form of oxygen is evaporated in tubes 29 and I23 than is supplied to the rectifier in an equivalent quantity of liquid nitrogen entering the top of the rectifier. The volume of pure liquid nitrogen delivered at the top of rectifier II equals approximately 55% of the volume of the liquid oxygen which is evaporated at the lower end of the rectifier. To ofi-set this difference, an additional quantity of reflux liquid enters the rectifier II through pipe I51. This additional liquid is equal to approximately 45% of the total liquid entering the rectifier II and consists of a mixture of approximately 47% oxygen and the balance nitrogen. This mixture is introduced onto the trays 23 at a point approximately midway between the top and bottom, where the liquid cascading from above has a similar composition to that entering through pipe I51.

The liquid nitrogen which condenses around tubes I23 and 29 collects in reservior 42 and fiows through metering tubes 43 and 44. Metering tube 43 is constructed to discharge approximately 60% of the liquid nitrogen collected in reservoir 42 through pipe I12 to the top of column II. Float valve I64 maintains a continuous fluid seal between rectifier I2 and rectifier II, so that no gas can fiow from rectifier I2, which has an internal pressure of four atmospheres, through pipe I12 to rectifier II, which hasa pressure of only one atmosphere.

Metering tube 44 is constructed to discharge "approximately 40% of the liquid nitrogen collected in reservoir 42, said discharge being directed to the top tray in rectifier I2, from which it cascades to the bottom of the rectifier. Air in gaseous form at a pressure of four atmospheres and'temperature of 178 C. is introduced into the rectifier I2 at the lower end thereof through pipe I52 from heat exchange I4. As the liquid nitrogen cascades over the trays 25 in the rectifier I2, it comes in contact with some of this air which contains 21% oxygen gas at the point of entry at the bottom of column I2. Some of the oxygen gas is progressively condensed in a manner similar to that described for rectifier II. The result is that air which enters rectifier I2 at the bottom is able to supply less volatile oxygen for replacement of part of the descending liquid nitrogen to the extent that the bottom tray will contain a mixture of approximately 47% liquid oxygen having a boiling point of approximately 178 C. If enough trays are used, all of the original 21% oxygen gas contained in the air will have been exchanged for nitrogen gas by the time the gas reaches the top tray in rectifier I2, so that pure nitrogen gas is all that remains to condense around tubes I23 and 29.

A small quantity of air is condensed in heat exchanger I4 and this liquid is conducted by a pipe I49 to a point in rectifier I2, where it will meet a liquid cascading over the trays that is of a similar composition and the combined liquids will continue to cascade to the bottom of the rectifier where the resulting liquid will contain 47% oxygen as described.

The liquid collecting in the bottom of the rectifier l 2 raises fioat I56 and discharges through pipe I51 to rectifier II. Float valve I55 serves to maintain a liquid seal and prevent the escape of gases from rectifier I2 in the same manner as float valve I64.

When the liquid nitrogen contained in reservoir I64 is allowed to pass through outlet I65, it is subjected to a drop in pressure. This drop in pressure lowers the boiling point of the liquid nitrogen, so escaping, about 12 C. The result is that a small amount of the liquid nitrogen immediately vaporizes to cool the body of the liquid to the lower boiling point occasioned by the drop in pressure. Pipe I12 therefore discharges into rectifier II a mixture of liquid nitrogen and gaseous nitrogen and the amount of nitrogen vaporized in this manner represents a loss of liquid to the column I 0. This loss is compensated for by-the fact that the nitrogen gas 11- discharging fromthe top of column II has a temperature 12 C. lower than is required to liquety air under a pressure of four atmospheres. The heat absorbing capacity of the nitrogen gas discharging through pipe I21 is therefore utilized by passing this gas through a coil 89 contained within the heat exchanger I4. Within this exchanger, the coil is surrounded by incoming air under a pressure of four atmospheres and some of this air is condensed, dropping to the bottom 01 the exchanger and discharging through pipe I49 to rectifier I2 wherein it is discharged through float valve I55 and pipe I51 to rectifier II Thus, a quantity of liquid reaches rectifier II which is equal to that lost by the partial vaporization of the nitrogen discharging into rectifier II through pipe I12.

In rectifier I2, the liquid discharging through fioat valve I55 is also subjected to a drop in pressure with the result that pipe I51 discharges a mixture of liquid and gas into rectifier II for the same reason that pipe I12 discharges a mixture of nitrogen gas and liquid nitrogen into rectifier II. This loss is also compensated for in a similar manner by an additional flow of cold gases through pipe I21 and coil 89 in heat exchanger I4 resulting in an additional compensating quantity of liquid being added to rectifier I2 through pipe I49.

When liquid oxygen collected in reservoir I59 is discharged through valve I62 into tubes I23 to be evaporated, it is subjected to a lower pressure induced by pump I14. The lower pressure in these tubes results in part of the liquid oxygen being evaporated to compensate for the lower boiling point of the liquid oxygen in the tubes. The result is that the oxygen gas passing through pipe I25 has a lower temperture than required to condense the air in exchanger I4, which is under a pressure of four atmospheres. This heat absorbing capacity of the cold oxygen gas discharging through pipe I25 is not very large and the small coil -88 placed in heat exchanger I4 condenses an additional part of the air passing therethrough, said condensate also entering rectifier I2 through pipe I49.

Air under a pressure of four atmospheres passes through heat exchanger I9 and is cooled in a manner which will be subsequently described, to a temperature of approximately 178 C. At this temperature and pressure, the air flows through pipe I38 to control valve I30. Control valve I30 is operated by the rise and fall of float I32 which responds to the rise and fall of the liquid in evaporator condenser I3 of column I0. As the supply of liquid in evaporator condenszr I3 decreases, valve I30 opens and permits the flow of air through ports I34 and I35 and pipe I39 to expansion engine I5. The refrigeration produced by expansion engine I results in an additional supply of liquid reaching the evaporator condenser I3 of column I0, as will be later described. As this additional liquid reaches the evaporator condenser I 3, valve I30 partially closes port I35 and restricts the flow of air to the expansion engine I5. Thus, expansion engine I5 operates continuously at a controlled speed which is directly in proportion to the requirements of evaporator condenser I3 for additional liquid to keep the column I0 in a state of thermal balance.

In order that piston I33 will operate freely in valve I30, it is necessary for a slight clearance to be maintained between the walls of the valve body I91 and the sides of the piston I 33. This slight clearance results in the escape of a small 12 3 quantity of high pressure air from ports I34 and I35. Said escaping air is discharged into the rectifier II at a point where the composition of the gas within the rectifier is approximately the same as said air discharged into the rectifier I I by valve I30. A small amount of air discharged into the column, as described, will be completely rectified without destroying the balance of the column or decreasing the purity of the products of the fractionation because of the fact that there is a quantity of pure liquid nitrogen flowing into the top of rectifier II through pipe I12 that is in excess of that required to wash down all of the oxygen gas normally present in the rectifier. The oxygen gas present in the leakage air discharging into rectifier II causes a loss of. evaporator liquid in condenser evaporator I3 equal to the quantity of said oxygen gas and this loss must be offset by additional refrigeration provided by expansion engine I5. Consequently, it is desirable to hold the leakage around piston I33 to a very minimum.

In order to compznsate for heat losses due to infiltration through the insulation and inefliciency in the operation of the apparatus, additional refrigeration is employed which is provided by the expansion engine I5.

Due to the fact that engine I5 is performing work, the expansion of the air in engine I5 materially cools the same. Because the air entering the engine is at a ,low temperature of 178 C., the expansion and additional cooling that takes place in the engine results in the air exhausting from the engine through pipe I45 having a temperature as low as 192 C. The exhaust air from engine I5 passes through pipe I45 into coil 9I located in the heat exchanger I4. Because the air surrounding coil 9| in heat exchanger I4 will begin to condense at a temperature of -l'77 C., due to its pressure of four atmospheres, the air from the engine absorbs heat and condenses air in heat exchanger I4 until it reaches a temperature of approximately -l78 C. at which temperature it leaves the heat exchanger I4 through pipe I41. Thus, some of the air in heat exchanger I4 is condensed. The air condensed by coil 9| in heat exchanger I4 drops to the bottom of the exchanger and flows through pipe I49 to rectifier I2. Thus, the expansion engine I5 indirectly supplies column I0 with the liquid necessary to compensate for the heat losses of the apparatus and operates automatically as required.

When air compressed to a pressure of four atmospheres flows through heat exchanger I4, it cannot be cooled to a temperature lower than 177 0., because at this temperature it begins to condense and any additional heat extracted from said air is supplied from the latent heat of the condensing air. For this reason, the cooling gases discharging from the coils 88 89 and 9I of heat exchanger I4 will be of a temperature only slightly colder than the compressed air surrounding the coils. The temperature of the gases flowing from the coils through pipes I41, I28 and I26 should be approximately -1'78 C. or about 1 C. colder than the compressed air surrounding the coils in the heat exchanger I4. Since the temperature of the gases discharged from coils 88, 89 and EH is above the liquefaction temperature of air at four atmospheres, it will be readily comprehended that no liquefaction of air takes place in either of the heat exchangers I9 or 2I.

The flow of the gases through the valves I8, I06

and 92 and through the heat exchangers I9 and 13 2| may be traced as follows: when the piston rod SI of valve mechanism I8 is in the position shown in Fig. 1, air is drawn into the inlet 49 of compressor I6, is compressed by the comprezsor to approximately four atmospheres and passes out through the outlet 5| and pipe 56 into the case 52 of the cooler II, where the cool water which flows through the coil 53 of said cooler brings the temperature of the compressed air back to approximately ambient temperature. The air so cooled and compressed passes through the pipe 51 and the branch pipe I8 into the cylinder 59 of the valve mechanism I8 and leaves the same through the port-14, flowing along conduit 85 of heat exchanger 2|. As the air flows along this conduit, the temperature thereof is progressively reduced, until it leaves valve mechanism I05 where it passes through chamber I09 and into chamber I I0, leaving said latter chamber through pipe I48 and entering the uppermost portion of the case 81 of heat exchanger I4. At the same time, oxygen gas flows through pipe I25, coil 88 and pipe I26 and through the conduit 86 of heat exchanger 2|, which is in heat-conducting relationship relative to the other two conduits. Also nitrogen gas fiows through pipe I21, coil 89, pipe I28 and to the valve mechanism I05. In said valve mechanism, the nitrogen enters chamber I08 through port H5 and flows through conduit 84 of heat exchanger 2|. The temperature of both the nitrogen and oxygen is about 1'78 C. on entering the heat exchanger 2|. Due to the fact that the weight of the oxygen and nitrogen entering the heat exchanger 2| is about equal to the weight of the air entering the same, and due to the fact that the air flows in a direction opposite to the direction of flow of the other gases in said heat exchanger, the corresponding temperatures throughout the heat exchanger will be substantially the same. Thus, the temperature of the air discharged from exchanger 2| would be about 1'77 C. which is the temperature at which air condenses at the pressure of four atmospheres. Also the nitrogen and oxygen leaving the exchanger are at substantially ambient temperature. The oxygen is removed from exchanger 2| by means of pump I74 which operates at a slight vacuum to maintain the pressure of the oxygen at slightly below the pressure of the nitrogen in column lI.

disposed of as desired.

The heat exchanger I9 functions similarly to the exchanger 2| with the terminal temperatures about the same. pansion engine 35 passes through pipe I45, coil 9|, pipe I l? and to the valve 92. In the said valve, this air enters chamber 95 through port IIlI and leaves said valve, flowing through conduit 8| of heat exchanger I9. The air, on leaving the heat exchanger I9, enters valve I8 through port 99 and is discharged from said valve to the atmosphere. A part of the air furnished by compressor I6 flows through branch pipe 'II, port 68 and port II of valve I8 and from this valve, through the conduit 82 of heat exchanger I9. The air, on leaving said heat exchanger, enters chamber 96 of valve mechanism 92, from which it flows through valve 99 and into pipe I38.

Pipe I138 conducts the air to the valve I39, from which it travels as previously described.

Since the air entering case 81 of heat exchanger I4 through pipe I48 is at the condensation temperature and pressure, the cooling done by coils 88, 89 and 9| will result in the formation The nitrogen leaves the 5 valve 58 through pipe 200 from which it may be Air discharging from the ex- III of condensate which travels through the app ratus as previously described.

When piston rod 6| of valve mechanism I8 is moved to the left of the position as viewed in Fig. l, by any suitable mechanism not shown, the air entering heat exchanger 2| is caused to travel along conduit 84 and the nitrogen caused to travel along conduit 85. Valve I05 automatically adjusts itself to the change in flow. Also, the incoming airentering the exchanger I9 is transferred from conduit 82 to conduit 8| and the outgoing air caused to travel through conduit 82. Likewise, valve 92 automatically adjusts itself to the change. Operation ofthe piston rod 6| is preferably performed periodically by automatic means, so that the transfer of flow is automatically accomplished at regular intervals.

Each time that the valve mechanisms attached to the heat exchangers I9, 2| operate, a small volume of compressed air is lost from one of the conduits to the atmosphere. For this reason, it is desirable that the volume of the conduits which comprise said heat exchangers be kept as low as practicable. The low pressure used by my invention helps to minimize this loss and with a good design of heat exchanger, the loss becomes negligible.

Air that is compressed has a capacity for holding water vapor that is approximately in inverse proportions to its volume. Thus, air at a pressure of one atmosphere has four times as much capacity for holding water vapor as it has after being compressed into a space one fourth as large in which confinement it would have a pressure of four atmospheres. The capacity of air to hold water vapor is also a function of its temperatures, the higher the temperature, the greater the capacity for holding water vapor. With these facts in mind, I will describe the manner in which water vapor contained in the atmosphere is eliminated from the critical parts of my invention where its presence would soon make the apparatus inoperative.

Air drawn into the intake 49 of compressor I6 may be of any degree of saturation, depending on the local atmospheric conditions. For the purpose of illustration, the relative humidity in the atmosphere may be considered to be of a percentage over 25%. The air, being compressed to a pressure of four atmospheres and cooled to viously described, and flows through one of the conduits 84 or 85 in heat exchanger 2| or in one of the conduits 8| or 82 of heat exchanger I9. As the compressed air flows through the conduit, it is progressively cooled. As it cools, the saturation point lowers and a film of moisture is deposited on the Walls of the heat exchanger. This continues until the temperature of the air has dropped so low that practically all of the water vapor has been deposited on the walls of the exchanger. As the air reaches the lower temperatures, the carbon dioxide present in small quantities is also deposited on the walls of the heat exchangers. After a short time interval, during which time the moisture and carbon dioxide deposited on the walls of the heat exchanger has formed nothing more than a thin film, the valve mechanisms I6, 92 and I located at each end 01' the exchangers are caused to operate in the manner previously described, so that the exhausting air and nitrogen pass through alternate conduits relative to the incoming compressed air. The exhaust air andnitrogen gases have previously been dehydrated when they passed into the apparatus through the heat exchangers.

when they pass through the exchangers on the way out of the apparatus, they are expanded to four times the volume they had when they went in, and they therefore have four times the capacity to absorb moisture that the ingoing compressed gases had to contain it. At each point in the length of the exchanger, the temperature of the outgoing gases is very close to the temperature of the incoming gases, so that the film deposited at each point along the walls of the heat exchangers is readily evaporated by the outgoing gases nd the apparatus is kept free from large deposits or solid water or carbon dioxide which would be detrimental to the continuing operation of the apparatus.

Having described the operation of my invention after it has reached a state of equilibrium and is operating at full capacity, I will now described the manner in which it automatically comes to full capacity from a warm start by merely starting the air compressor into operation.

Air compressor I6 and oxygen compressor I14 are started simultaneously. The column I0 and the entire apparatus may be considered at ambient temperature. For this, reason, there will be no liquid anywhere in the apparatus. Float valves I55, I62 and I66 will remain closed against their seats. Float I32 will fall against a stop 232 at which position ports I34 and I35 of valve I30 will be in full communication, permitting a maximum quantity of air to reach expansion engine I5. As the only air which can pass through the system at this time is that which passes through the engine, it will be necessary to provide an engine capable of absorbing the entire output from compressor I6, or as an alternate method, compressor I6 can be regulated by an automatic pressure governor, not shown in the drawings, which would provide a constant output of air under pressure from compressor I6, regardless of the quantity air required.

As previously stated, the only place that the air can flow when the apparatus is first put in operation, is through the expansion engine and out through the coil 9| in heat exchanger I4 and through heat exchanger I9. The cooling affect produced in the expansion engine is not enough to liquefy the air at first, but the cool exhaust air flowing through the exchangers cools the incoming air which is further cooled by expansion in a continuously regenerative cycle'until the air expanding from the engine which passes through coil 9I reaches a temperature of -l'l7 C. When this temperature is reached, air surrounding coil 9I begins to condense, flowing through pipe I49 into rectifier I2 where it descends, filling reservoir I53 and opening float valve I55 From there, the liquid air fiows through pipe I 51 to rectifier I I, where it cascades over the lower of trays 23 and collects in reservoir 35. The very first quantities of liquid collecting in reservoir 35 are distributed in the correct proportions as previously described, by metering tubes 36 and 31. The liquid air discharging from tubes 36 and 31 flows into tubes I23 and 29, cooling the same and causing air to start condensing on the outside of said tubes because of the higher air pressure on the outside.

side of tubes I23 and 29 collects in reservoir 42, where it is immediately separated into two streams of the correct proportions by metering tubes 43 and 44. Part of the liquid is thus deposited on the top of trays 25 in rectifier I2 and part of said liquid fills reservoir I64. After filling said reservoir I64, the liquid passes through valve I66 and pipe "2 to the top of rectifier II, where it cascades over trays 23, cooling and filling the same. As the column I0 is gradually cooled to operating temperature, the gases exhausting through coils B8 and 39 begin to help the expansion engine in the production or liquid air in the heat exchanger I While the column I0 is being cooled down and the various parts ar being filled with liquid, the liquids in all parts of the system are of mixed composition. Th first place that rectification begins to take effect is in rectifier I2, where the air passing upwardly over trays 25 begins to lose more and more of its oxygen and the liquid collecting in reservoir 42 increases its nitrogen content until pure nitrogen is being collected. As ure nitrogen begins to flow through pipe II2 into rectifier II, the process of rectification begins to take place in this rectifier and the liquid collecting in reservoir 35 becomes oxygen of increas ingly high purity, until a. state of equilibrium is reached.

When reservoir I29 becomes filled with liquid, float I32 raises and expansion engine I5 is throttled until it is providing just enough refrigeration to keep the entire apparatus in a state of perfect balance.

The normal composition of the atmosphere contains 94% of argon and minute traces of other inert gases. In the operation of the rectifier II, it is possible to adjust the proportionate fiow of metering tubes 36 and 31, so that the argon, which has a boiling point below oxygen and above nitrogen, can be caused to leave the apparatus as an impurity of either the oxygen or th nitrogen, depending upon which of the products of the fractionation is desired in the highest state of purity. Where the argon must be eliminated from both the nitrogen and oxygen, an additional rectifying apparatus, not shown on the drawings, would have to be provided.

In Fig. 3, I have shown a modification of the invention in which only oxygen is collected and in which the nitrogen is wasted. Inasmuch as this apparatus is similar to that shown in Fig. l, the description of the corresponding parts will not be repeated and the same reference numerals, to which the sufllx a has been added, will be used to designate corresponding parts.

In the form of the invention shown in Fig. 3, the heat exchanger I9 is dispensed with. In this case, the pipe I38, which was connected to the valve 92, is directly connected to the pipe I 48, which leads to the valve I05. Similarly, th pipe I41, which was connected to valve 92, is directly connected to the pipe I28 which also leads to the valve I05. At the same time, the valve 92 and the portion of the valve I8 including cylinder 58, pistons 62 and 63, and branch pipes TI and I8 are dispensed with, and pipe 5! from the cooler I'I being connected directly to the port I2 of valve mechanism I8.

The result is that the supply of air for both the rectifying column I0 and air expansion engine I5 pass through the same conduit in heat exchanger 2| and the exhaust air from expansion engine I5 -and the nitrogen from column 17 II are mixed and pass through a single conduit in heat exchanger II in counterfiow to the incoming air.

When heat exchangers l9 and 2| are combined into a single heat exchanger, such as shown by heat exchanger 2| in Fig. 3, the principle of operation remains the same. This is true because the gases flowing in opposite, directions have equal mass. Th same temperatures prevail as when two heat exchangers, such as I! and 2|, are used, the only difference being that when one heat exchanger is used, the air discharging from th expansion engine pollutes the nitrogen, making it unsuitable for use. The single heat exchanger 2|, shown in Fig. 3 would always be used where oxygen gas alone was the only product desired from the fractionating process.

The advantages of my invention are manifest. By metering the liquids formed from the constituents of the air, the device becomes entirely automatic and does not require adjustment. When the apparatus is used on aircraft at different altitudes, a wide variation of exhaust pressures below the normal sea level pressures will be automatically compensated for and the apparatus will continue to function satisfactorily without manual attention.

It is common practice in the operation of conventional fractionating apparatus to expand most of the air handled before passing it into the rectifying column. In order to permit a satisfactory expansion ratio, the air must be compressed to a pressure several times the pressure used in the rectifier. with my invention, the air which is expanded for refrigeration purposes is not used for supplying the rectifier, and the amount of pressure required at the rectifier is also ample for the expansion engine. Because the volume of air required in the expansion en- 'gine is quite low compared to the total volume of air handled and because all of the air used in the apparatus requires a pressure of only four atmopheres, the total power requirements are as low as is theoretically possible.

The low operating pressures made possible by the use of my invention also permit the use of diaphragm type air compressors which have very little friction in their working parts and add considerable to the over all efliciency of the apparatus. The use of a diaphragm type air compressor also eliminates possibility of the air picking up oil vapors. These 011 vapors, if present, are liable to accumulat in the rectification column at the same place as the liquid oxygen and upon reaching a certain concentration, are liable to result in an explosion. Elimination of the explosion hazard makes the apparatus suitable for use on aircraft or in public buildings or places where safety precautions must b observed. It is merely necessary to energize the apparatus and the apparatus will deliver substantiall pure oxygen after the same has run for a predetermined length of time. The apparatus is particularl useful for portabl Welding units, in aeroplanes designed to travel at a high altitude, and in hospitals and in like places where oxygen in not too great quantities is required for immediate consumption.

Changes in the specific form of my invention, as herein described, may be made within the scope of what is claimed without departing from the spirit of my invention.

Having described my invention, what I claim as new and desire to protect by Letters Patent is:

l. The method of fractionating a gas mixture such as air in a gas i'ractionating apparatus including an evaporator for oxygen, said method comprising compressing and cooling the air, introducing the compressed cooled air into the fractionating apparatus, separating the constituents of the air, cooling of the constituents by the evaporation of liquid oxygen within the evaporator, expanding with external work a separate portion of compressed cooled gas to produce refrigeration, utilizing said refrigeration for cooling the air introduced into the fractionating apparatus discharging the expanded air to the atmosphere and controlling the volume of air expanded by the level of theliquid oxygen in said evaporator.

2. The method of fractionatlng a gas mixture such as air in a rectifying column which comprises compressing the air, cooling the compressed air to the condensing point, liquefying a portion or the cooled air, separating the liquefied portion from the gaseous portion, introducing the gaseous portion into said rectifying column at the lower end thereof and directing the same upwardly through the column, producing in the column liquid nitrogen and directing the same downwardly through the column in counter flow with the gaseous portion of air, to produce an oxygen enriched liquid fraction at the lower end of the column, introducing the liquid portion of the air into the column at an intermediate point in the column and further fractionating said oxygen enriched liquid fraction.

3. The method of fractionating air by rectification in two stages, and by heat exchange in an evaporator condenser which comprises cooling and compressing the air to. such a pressure that the nitrogen separated under that pressure in the first stage of rectification can be liquefied in heat-exchange with oxygen vaporizing in the evaporator condenser, separating the liquefied nitrogen into two parts of fixed volumetric ratio, utilizing one of said parts as a refiux liquid in the first stage of rectification to produce a liquid fraction rich in oxygen and utilizing the other of said parts at reduced pressure in the second stage of rectification as a reflux liquid to produce a liquid fraction of substantially pure oxygen and a gaseous fraction oi substantially pure nitrogen.

4. The method of fractionating air by rectification in two stages, which comprises cooling and compressing the air, separating under pressure in the first stage of rectification two liquid fractions, one rich in oxygen and the other consisting of substantially pure nitrogen, introducing the nitrogen fraction at reduced pressure to the second stage of rectification as a reflux liquid, introducing the oxygen rich fraction at reduced pressure into the second stage of rectification to produce in said second stage a fraction of substantially pure oxygen, and dividing the liquid oxygen fraction into two proportionate parts, bringing each of said parts separately into heat exchange relation with the nitrogen of the first stage to produce vaporization of said parts and condensation of the nitrogen, withdrawing one of the vaporized parts of the oxygen from the apparatus and utilizing the second vaporized part for coaction with the reflux liquid in the second stage to produce a substantially pure nitrogen gas fraction and the liquid oxygen fraction in the second stage.

5. In a gas fractionating apparatus, means for producing a fractionated liquid from the gas to be fractionated, a receptacle therefor, a number of vertically extending conduits within the re- 19 ceptacle and leading therefrom, said conduit: having longitudinally extending slits therein, said slits having definite relative widths to produce -in said conduits substantially fixed volumetric relation of the flow therethrough and means for utilizing the separate liquid streams from each conduit in the fractionating of the gas.

6. In a gas fractionating apparatus for .tractionating air, a compressor for compressing the air, heat exchange means for cooling the compressed air, rectifying means for producing an oxygen fraction from the cooled compressed air, an expansion engine, means for conducting a portion of the compressed cooled air through said expansion engine and into said heat exchange means, to further cool the incoming compressed air, and control means for controlling the output from said expansion engine in direct relation to the amount of said oxygen fraction available in said rectifying means.

'i. In a gas fractionating apparatus for fractionating air, a compressor for compressing the air, heat exchange means for cooling the compressed air, rectifying means for producing a liquid oxygen fraction from the compressed air, a receptacle therefor, an expansion engine, means for conducting a portion of the compressed cooled air through said expansion engine and into said heat exchange means, to further cool the incoming compressed air, and control means dependent for operation upon the height of the liquid oxygen in said receptacle for controlling the output of said expansion engine.

8. In a gas fractionating apparatus for fractionating air, a first rectifier, a second rectifier, a condenser therebetween, means for directing cold air into said first rectifier, a receptacle for a liquid rich in oxygen at the lower end of said first rectifier, means for conducting such liquid to the second rectifier, a receptacle for liquid nitrogen at the upper end of said first rectifier, and communicating with said condenser, dividing means for dividing the liquid nitrogen and for directing a portion of the same into the upper end of said first rectifier and the remainder into the upper end of said second rectifier, a receptacle ior liquid oxygen at the lower end of said second rectifier and dividing means for dividing the liquid oxygen into two portions and a conduit for directing a portion of the same into said condenser and the remainder thereof exteriorly of said rectifier.

9. In a gas fractionating apparatus for fractionating air, a first rectifier, a second rectifier, a condenser therebetween divided into a first section and a second section, the first section communicating with the second rectifier and the sec-- mid section with the exterior, means for directing cold air into said first rectifier, a receptacle for a liquid rich in oxygen at the lower endof said first rectifier, means for conducting such liquid to the second rectifier, a receptacle for liquid nitrogen at the upper end of said first rectifier and communicating with said condenser, dividing means for dividing th liquid nitrogen and for directing a portion or the same into the upper end of said first rectifier and the remainder into the upper end of said second rectifier, a receptacle for liquid oxygen at the lower end of said second rectifier, and dividing means for dividing the liquid oxygen and for directing a portion of the same into the first section of said condenser and the remainder thereof into the fier having a heat exchange chamber therein, a receptacle for a liquid fraction of the gas to be fractionated, two conduits leading from the receptacle, proportional dividing means for restricting the fiow through both of said conduits to cause division of the liquid into two streams, one of said conduits discharging into said chamber.

11. In a gas fractionatingapparatus, a rectifier having a heat exchange chamber therein, a receptacle for a liquid fraction of the gas to be fractionated, two vertically extending conduits within the receptacle and leading therefrom, said conduits having longitudinally extending slits therein of predetermined form to cause division of the liquid, one of said conduits discharging into said chamber.

12. In an air iractionating apparatus producing liquid air, two rectifiers, means for directing the liquid air into one of said rectifiers, an evaporator condenser associated with said rectifiers, said evaporator condenser serving to produce a liquid rich in nitrogen, a receptacle for said liquid, means for dividing the liquid in said receptacle into separate portions of substantially fixed volumetric ratio, means for directing one of said portions into the other rectifier for heat exchange therein to produce a liquid rich in oxygen, means for directing the other portion of said second named liquid into said first named rectifier for heat exchange with the air therein to produce a nitrogen gas for circulation through said evaporator condenser, means for dividingthe third named liquid into separate portions of substantially fixed volumetric ratio and means for directing one of said portions of said third named liquid into said evaporator condenser for heat exchange to cause vaporization of the liquid rich in oxygen and the production of o ygen gas and liquifaction of the nitrogen gas entering said evaporator condenser from said first named rectifier.

13. In an air fractionating apparatus continuously producing liquid air, two rectifiers, means for directing the liquid air into one of said rectifiers, an evaporator condenser associated with said rectifiers, said evaporator condenser serving to produce a liquid rich in nitrogen, dividing means for dividing the liquid as formed into two streams having substantially fixed volumetric ratio, means for directing one of said streams into the other rectifier, said other rectifier continuously producing a liquid rich in oxygen, means for directing the other portion of said second named liquid into said first named rectifier for heat exchange with the air therein to produce nitrogen gas for circulation through said evaporator condenser, means for dividing the third named liquid as formed into two streams havin substantially fixed volumetric ratio and means for directing one of said streams of said third named liquid into said evaporator condenser for heat exchange to cause vaporization of the oxygen therein and liquifaction of the nitrogen gas entering said evaporator condenser from said first named rectifier.

14. In an air fractionating apparatus, continuously producing liquid air, two rectifiers, means for directing the liquid air into one of said rectifiers, an evaporator condenser associated with said rectifiers, said evaporator condenser serving to produce a liquid rich in nitrogen, a receptacle therefor, two vertically extending conduits within the receptacle and leading therefrom, said conduits having longitudinally extending slits therein, said slits being formed to produce a substantially fixed volumetric ratio of flow into the conduits, means for directing the liquid from one 01' said conduits to the other rectifier, means for directing the other portion of said second named liquid into said first named rectifier for heat exchange with the air therein to produce nitrogen gas for circulation through said evaporator condenser, said other rectifier continuously producing a liquid rich in oxygen, a receptacle therefor, two vertically extending conduits within said receptacle and leading therefrom, said conduits having longitudinally extending slits therein, said slits being formed to produce a substantially fixed volumetric ratio of fiow into said conduits, one of said conduits discharging into said evaporator condenser for heat exchange to cause vaporization 01' the oxygen therein and liquifaction of the nitrogen gas entering said evaporator condenser from said first named rectifier.

RICHARD T. CORNELIUS.

REFERENCES CITED The following references are of record in the 35 file of this patent:

22 unrran s'rxms mm Number Name Date 1,093,859 Johnson Apr. 21, 1914 1,539,450 Wilkenson May 26, 1925 1,607,321 Van Nuys Nov. 16, 1926 1,785,491 Messer Dec. 16, 1930 1,842,263 Gobert Jan. 19, 1932 1,853,236 Shadle Apr. 12, 1932 1,956,495 DeBaufre Apr. 24, 1934 1,970,299 Frankl Aug. 14, 1934 2,062,781 DeBaufre Dec. 1, 1936 2,089,558 Karwat Aug. 10, 1937 2,116,191 DeBaufre May 3, 1938 2,217,467 Bonnaud Oct. 8, 1940 2,240,925 DeBauIre May 6, 1941 2,252,739 Stoever Aug. 19, 1941 2,256,421 Borchardt Sept. 16, 1941 2,321,445 Yendall et a]. June 8, 1943 2,327,459 Rice Aug. 24, 1943 2,446,535 Fausek et a1 Aug. 10, 1948 FOREIGN PATENTS Number Country Date 469,943 Great Britain Aug. 3, 1937 OTHER REFERENCES Ruhemann, The Separation of Gases," 1940; The Clarendon Press; Oxford, England. 

